The Japanese traditionally used natural sharpening stones lubricated with water (using oil on a waterstone reduces its effectiveness.) They have been doing this for many hundreds of years.
Generally speaking the Grit one would use is as follows:
- Less than 1000 grit is typically used to repair knives with chipped edges.
- 1000 to 3000 grit are used to sharpen dull knives.
- 4000 to 8000 grit are finishing stones and are used to refine your knife edge.
Most stores carry a range of Whetstones across the Grit spectrum.
This includes Brands such as Yaxell out of Japan.
Please check with your local store about availability